In a small bowl, whisk together pineapple juice, lime juice and 3 tablespoons oil.

In another small bowl, whisk together all of the spices. Add half of the spice mixture to the pineapple juice mixture and stir to combine.

Add the beef to a large, ziptop bag. Pour the pineapple juice marinade over and seal. Refrigerate for 4-6 hours, or overnight.

Heat remaining tablespoon of oil in a large skillet over medium-high heat. Drain marinade from beef and add beef to pan, along with the peppers, onions, pineapple and remaining spice mixture. Cook, stirring often, until everything is charred and the vegetables are crisp tender. (If the pan is crowded, cook in two batches, then return everything to the skillet before adding the cheese).

Preheat broiler. Remove skillet from heat and top with shredded cheese. Place under broiler for about 2 minutes, or until cheese is melted and bubbly.

Serve in warm flour tortillas with guacamole and sour cream.